The present invention relates to a knee bolster system and more particularly to an extendable and retractable knee bolster system, including its control logic, with an impact pre-sensing system for an automotive vehicle.
The fixed fore-aft location of a knee bolster may constrain how far the lower portion of the instrument panel can be placed forward and away from the knees of an occupant. This constraint can limit comfort for the occupant. The position of current fixed-in place knee bolster systems is also a constraint on interior spaciousness. It is known that utilization of inflatable knee bolster systems brings the location of the lower portion of the instrument panel rearward when preferred. However, such crash triggered inflatable knee bolster systems do not typically retract automatically, and could require complete replacement after actuation. Such replacement is expensive, a cost borne by the consumer.
In accordance with the present invention, there is provided an extendable and retractable knee bolster system generally positioned in the lower portion of the instrument panel of a vehicle at knee height to an occupant. The knee bolster system has at least one and preferably two telescoping mechanisms secured to a bolster pad. The telescoping mechanism has an outer tube securing rigidly to the vehicle structure at a base end. The outer tube concentrically supports an inner tube capable of linear telescoping movement. The inner tube has a leading end secured to the bolster pad and a trailing portion engaged to a shuttle which operatively connects to a drive device via a rotating screw disposed concentrically within the inner and outer tubes.
The drive device rotates the screw which is engaged threadably to the shuttle. The shuttle thereby moves or extends the inner tube through a free end of the outer tube. The shuttle comprises part of a plowing mechanism which can help dissipate the energy. Preferably, the plowing mechanism has at least one axially extending groove defined by an outer cylindrical surface of the inner tube and facing an inner cylindrical surface of the outer tube. The groove has a trailing deep end and a leading shallow end. A sphere resides in the deep end and is restricted there during normal extending and retracting motions of the knee bolster pad by a plurality of radially extending fingers engaged to the shuttle. During an impact on the bolster pad, the sphere is thrust into the shallow end and plows into the inner surface of the outer tube causing deformation of the outer tube. The kinetic energy from the impact upon the bolster pad is absorbed into the telescoping mechanism. Examples of ways in which this energy could be absorbed are plowing of the balls and deformation of the tubes.
Preferably, the knee bolster system is actuated or controlled by a microprocessor which electrically communicates primarily with a plurality of risk sensors and a plurality of imminent impact sensors, and secondarily with a plurality of impact occurrence sensors. By using the outputs of risk sensors and imminent impact sensors as the primary means of triggering deployment, deployment times in the tenths of a second for the extendable/retractable knee bolster invented here rather than thousandths of a second required for impact triggered systems that have been proposed by others are tolerable in some applications. If a fully robust pre-impact sensor is not available, the bolster will automatically extend to the current mandated bolster location if the occupant is unbelted and the car placed in gear. The knee bolster pad will automatically retract if the ignition is off or the transmission is not in gear. In addition, the bolster pad will automatically retract if output signals or setpoints which caused the initial extension are cleared.
An advantage of the present invention is that through the use of continuous monitoring and forecasting, the knee bolster is able to be stored further from the occupant in so doing permitting a more spacious vehicle interior.
Another advantage of the present invention is the automatic retraction capability thereby minimizing maintenance costs.
An additional advantage of this invention is the enhancement of vehicle entry and egress, since the bolster is stowed when the vehicle is not in gear.